1. Field of the Invention
The present invention relates generally to a temperature compensating optical waveguide device, and particularly to a temperature compensating optical waveguide device for fiber Bragg gratings.
2. Technical Background
Fiber Bragg gratings are widely used in optical communication systems. The center wavelength of a fiber Bragg grating changes with temperature and strain. A typical fiber Bragg grating experiences an upward shift of about 10 picometers per degree centigrade above its nominal operating temperature in the operational temperature regime generally specified for optical communication systems. Like wise, a typical fiber Bragg grating experiences a shift in center wavelength of about 0.1 picometer per psi of tensile stress.
Modern optical communication systems require that fiber Bragg gratings operate at or near a single center wavelength over a specified temperature range. A number of approaches have been proposed to athermalize fiber Bragg gratings. These approaches include mounting the fiber Bragg grating to a substrate having a negative coefficient of thermal expansion and bending the fiber. Both of these approaches have inherent difficulties that impair their operational performance. For example, negative expansion substrates typically require hermetic packaging to prevent degradation of operation characteristics due to environmental factors and systems that employ bending of the fiber to reduce tensile stress pose many manufacturing and long term stability challenges. Therefore, there is a need to develop an easily robust temperature compensating optical waveguide devices that is easy to manufacture and deploy.
One embodiment of the present invention is a temperature compensating optical waveguide device. The temperature compensating optical device includes a substrate. The substrate has a first end and a second end. The temperature compensating optical waveguide device also includes a first mount coupled to the first end and a second mount coupled to the second end. The temperature compensating optical waveguide device further includes an optical waveguide fiber coupled to the first mount and the second mount; wherein the optical waveguide fiber includes a Bragg grating.
In another aspect, the present invention includes a temperature compensating optical waveguide device. The temperature compensating optical waveguide device includes a substrate having a first coefficient of thermal expansion. The temperature compensating optical waveguide device further includes a first mount coupled to the substrate; the first mount having a second coefficient of thermal expansion. The temperature compensating optical waveguide device further includes a second mount coupled to the substrate; the second mount having a third coefficient of thermal expansion. The temperature compensating optical waveguide device also includes an optical waveguide fiber coupled to the first mount and the second mount; wherein the optical waveguide fiber includes a Bragg grating.
In another aspect, the present invention includes a temperature compensating optical waveguide device. The temperature compensating optical waveguide device includes a first member, the first member having an inner wall defining a cavity, wherein the first member has a first coefficient of thermal expansion. The temperature compensating optical waveguide device further includes a first mount coupled to the first member. At least a portion of the first mount is disposed within the cavity. The first mount has a second coefficient of thermal expansion different from the first coefficient of thermal expansion. The temperature compensating optical waveguide device further includes a second mount coupled to the first member. At least a portion of the second mount is disposed within the cavity. The second mount has a third coefficient of thermal expansion equal to the second coefficient of thermal expansion. The temperature compensating optical waveguide device further includes an optical waveguide fiber coupled to the first mount and the second mount, wherein the optical waveguide fiber has a Bragg grating.
In another aspect, the present invention includes a temperature-compensated optical waveguide fiber device. The temperature-compensated optical device includes a substrate having a first coefficient of thermal expansion. The substrate includes a first end and a second end. The temperature-compensated optical waveguide fiber device further includes a first fiber mount coupled to the first end of the substrate. The first fiber mount includes a first fiber-receiving groove and a first recess intersected by the first fiber receiving groove. The first fiber mount has a second coefficient of thermal expansion greater than said first coefficient of thermal expansion. The temperature-compensated optical waveguide fiber device further includes a second fiber mount coupled to the second end of the substrate. The said second fiber mount includes a second fiber-receiving groove and a second recess intersected by the second fiber-receiving groove. The second fiber mount has a third coefficient of thermal expansion greater than the first coefficient of thermal expansion. The first fiber-receiving groove and the second fiber-receiving groove are substantially aligned one to another. The temperature-compensated optical waveguide fiber device further includes an optical waveguide fiber device including a grating region, wherein the optical waveguide device is coupled to the first fiber mount and the second fiber mount, and the grating region is disposed between the first fiber mount and the second fiber mount. The grating region of the optical waveguide device has an operational center wavelength and the grating region is under tensile stress. The operational center wavelength varies less than +/xe2x88x920.04 nanometers as said device is thermally cycled between about xe2x88x9210xc2x0 C. and about 80xc2x0 C.
In another aspect, the present invention includes a temperature-compensated optical fiber device. The temperature-compensated optical fiber device includes a cylindrical member having a groove extending longitudinally in the cylindrical member. The temperature-compensated optical fiber device further includes a first fiber mount coupled to the cylindrical member, wherein the first fiber mount is disposed in the groove. The temperature-compensated optical fiber device further includes a second fiber mount coupled to the cylindrical member, wherein the second fiber mount is disposed in the groove and is spaced apart from the first fiber mount. The temperature-compensated optical fiber device further includes an optical fiber device coupled to the first fiber mount and the second fiber mount, wherein the portion of the optical fiber device disposed between the first fiber mount and the second fiber mount is under tension. The cylindrical member, the first fiber mount and the second fiber mount each have a respective coefficient of thermal expansion. The respective coefficients of thermal expansion of the cylindrical member, the first fiber mount and the second fiber mount are selected so that the optical characteristics of said optical fiber device remain substantially unchanged from about xe2x88x9210xc2x0 C. to about 80xc2x0 C.
The temperature compensating optical waveguide device of the present invention results in a number of advantages over prior art temperature compensating optical waveguide devices. For example, the present invention does not require hermetic packaging.
Another advantage of the present invention is that it may be fabricated from readily available materials having well known properties.
Another advantage of the present invention over prior art temperature compensating optical waveguide devices is that thermal response characteristics of the may be adjusted after initial assembly of the temperature compensating optical waveguide device.
Another advantage of the present invention is that the lengths of the components used to assemble an embodiment of the present invention are not required to posses a high degree of accuracy.
Another advantage of the present invention is that the shift in center wavelength of the grating is minimized by tensioning the grating during assenbly.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.